139
5.5.1 Calculation of Gross Primary Production,
Decomposition, and Respiration in Seawater
We performed an incubation experiment using seawater sampled in the north salt
marsh of the bird sanctuary site to model gross primary production (GPP) of phytoplankton and the respiration/decomposition in the water column by using the light
and dark bottle method. Although both GPP and respiration/decomposition occur in
the light bottles, it is assumed that only respiration/decomposition occurs in the dark
bottles. Therefore, rate of GPP and respiration/decomposition were calculated based
on the changes in dissolved inorganic carbon (DIC) concentration in the light and
dark bottles:
G
C C
C
C
t
=
-
(
-
(
)
é ë
ù û
l
l
d
d
1
2
1
2
/
(5.3)
R C
C
t
=
-
(
)
d
d
,
2
1 /
(5.4)
where G is the rate of GPP, C l1 and C d1 represent the DIC concentrations in the light
and dark bottles at the beginning of incubation, R is the rate of respiration/decomposition, C l2 and C d2 are those at the end of incubation, and t is incubation time.
Generally, G has been estimated by the change in dissolved oxygen concentration,
but this is merely an estimate calculated by using an arbitrary respiratory quotient.
So, in this study, G was evaluated by measuring DIC changes directly.
Figure 5.6a shows the relationship between G per unit chlorophyll a (G p ) and
photon flux density (I). At each water temperature, G p increases as photon flux density increases until I is around 200–600 μmol m
−2
s
−1
, but then G p decreases at
higher photon flux densities. In addition, under the same photon flux density
Photon flux density: I (μmol/m 2 /sec)
G
p
(mg C min -1
μgChl.a -1
)
0
1
2
3
4
5
0
10
20
30
40
0
2
4
6
0
250
500
750
1000
10ºC
20ºC
30ºC
R
(mgC m -3
min -1
)
Water temperature: T (°C)
(a)
(b)
y = 0.441e 0057x
R 2 =0.99
Fig. 5.6 Relationships between (a) gross primary production per chlorophyll a (G p ) and photon
flux density, and (b) respiration/decomposition (R) of seawater and water temperature. (From Endo
and Kawasaki 2017)
5 Carbon Storage in Tidal Flats
5.5.1 Calculation of Gross Primary Production,
Decomposition, and Respiration in Seawater
We performed an incubation experiment using seawater sampled in the north salt
marsh of the bird sanctuary site to model gross primary production (GPP) of phytoplankton and the respiration/decomposition in the water column by using the light
and dark bottle method. Although both GPP and respiration/decomposition occur in
the light bottles, it is assumed that only respiration/decomposition occurs in the dark
bottles. Therefore, rate of GPP and respiration/decomposition were calculated based
on the changes in dissolved inorganic carbon (DIC) concentration in the light and
dark bottles:
G
C C
C
C
t
=
-
(
-
(
)
é ë
ù û
l
l
d
d
1
2
1
2
/
(5.3)
R C
C
t
=
-
(
)
d
d
,
2
1 /
(5.4)
where G is the rate of GPP, C l1 and C d1 represent the DIC concentrations in the light
and dark bottles at the beginning of incubation, R is the rate of respiration/decomposition, C l2 and C d2 are those at the end of incubation, and t is incubation time.
Generally, G has been estimated by the change in dissolved oxygen concentration,
but this is merely an estimate calculated by using an arbitrary respiratory quotient.
So, in this study, G was evaluated by measuring DIC changes directly.
Figure 5.6a shows the relationship between G per unit chlorophyll a (G p ) and
photon flux density (I). At each water temperature, G p increases as photon flux density increases until I is around 200–600 μmol m
−2
s
−1
, but then G p decreases at
higher photon flux densities. In addition, under the same photon flux density
Photon flux density: I (μmol/m 2 /sec)
G
p
(mg C min -1
μgChl.a -1
)
0
1
2
3
4
5
0
10
20
30
40
0
2
4
6
0
250
500
750
1000
10ºC
20ºC
30ºC
R
(mgC m -3
min -1
)
Water temperature: T (°C)
(a)
(b)
y = 0.441e 0057x
R 2 =0.99
Fig. 5.6 Relationships between (a) gross primary production per chlorophyll a (G p ) and photon
flux density, and (b) respiration/decomposition (R) of seawater and water temperature. (From Endo
and Kawasaki 2017)
5 Carbon Storage in Tidal Flats